This invention relates to fastening arrangements for joining car body components, particularly car body components which are made of sheet metal, which include a locating surface on which the car body components can be supported and compression elements cooperating with a pneumatic and/or hydraulic pressure membrane for pressing the car body components against each other or against the locating surface.
A fastening arrangement of the type mentioned above is disclosed in German Offenlegungsschrift No. 196 22 575. With such a fastening arrangement two pieces of sheet metal of a car body, for example, can be pressed against each other so that they can be welded together along a connecting seam. When the sheets are to be welded together by a laser or an electron beam, the two sheets must be pressed against each other firmly enough that any waviness in the sheets is sufficiently minimized that a gap of preferably less than 0.2 mm remains between the sheets. The fastening arrangement described in this reference has, within each of a plurality of hollow bodies, a substantially tubular extensible element that can be acted upon by pneumatic or hydraulic fluid under pressure to force cylinders out of the hollow body, which then exert local pressure on, for example, the upper one of the two metal sheets. Because the hollow bodies are rigid and the cylinders acting on the surface of the sheet must have a minimum spacing, three-dimensionally shaped sheets cannot as a rule be pressed against each other sufficiently by the previously known fastening arrangements that they can be welded together by a laser or an electron beam to produce a connecting seam of the desired quality.
Accordingly, it is an object of the present invention to provide a fastening arrangement for joining car body components which overcomes disadvantages of the prior art.
Another object of the invention is to provide a fastening arrangement for joining car body components in which car body components can be pressed against each other uniformly and firmly enough so that welding of car body components, especially by a laser or an electron beam, produces a connecting seam of good quality.
These and other objects of the invention are attained by supporting plurality of compression elements and a pressure membrane on a fastening component that is movable in a direction toward a locating surface and can be fixed in relation to the locating surface. Preferably, the fastening component can be moved along the greater part of the path of motion toward the locating surface which is required for fastening, so that the compression elements need only be moved by the compression membrane along a short residual path. Consequently, the pneumatic and/or hydraulic pressure system and the pressure membrane can be made smaller and more simple and hence more inexpensive. In addition, moving the car body components to be joined into and out of the device is simplified. The arrangement according to the invention makes it possible for car body components such as, for example, sheet metal components, to be pressed against each other with little or no gap in a simple fashion.
Advantageously, the fastening component is capable of pivoting in relation to the locating surface about a lockable rotary joint. With this arrangement, motion of the fastening component along the main fastening path by simple pivoting of the fastening component in relation to the locating surface is possible. It is, of course, alternatively possible, for example, to make the fastening component linearly movable toward and away from the locating surface.
According to a preferred embodiment of the present invention, a hollow body which can accommodate a pressure membrane, preferably in the form of a tubular extensible element, is attached to the fastening component and the tubular extensible element is capable of being coupled to a pneumatic and/or hydraulic pressure line.
According to one embodiment of the present invention, the hollow body has a U-shaped cross section and is open on the side facing the locating surface so that the pressure membrane can act on portions of the compression elements adjacent to the open side. In this case, the compression elements advantageously are pivotally attached to the hollow body and desirably have at least a substantially L shape, with one leg extending approximately parallel to the locating surface and another leg extending approximately perpendicular to the locating surface. The ends of the approximately perpendicular legs compression elements facing the location surface are formed with a compression curve in order to avoid depressions in the surface of the car body components due to bearing pressure applied by the leg ends. The point of engagement of the pressure membrane and the legs extending approximately parallel to the locating surface preferably is located near the articulated connection of the legs to the hollow body, so that a relatively small motion produced by extension of the pressure membrane causes a relatively large motion of the legs extending approximately perpendicular to the locating surface.
The compression elements advantageously are mounted substantially close together in a direction which is perpendicular to the legs and approximately parallel to the locating surface, and the width of the legs is dependent on the waviness of the car body components. The fact that the compression elements are mounted close together assures that, even in the case of high residual waviness of the car body components, the gap between the surfaces of the components at each point of the planned weld seam is satisfactorily minimized. The width of the compression elements, which may alternatively be variable along the contour of the planned wield seam, may be appropriately selected according to the waviness produced by the roughly three-dimensional shape of the car body components.
According to an alternative embodiment of the invention, the hollow body has a substantially rectangular cross section and the side of the hollow body facing the locating surface has orifices for guiding the compression elements. In this case, the compression elements advantageously constitute pressure cylinders, each of which has a head that cooperates with the pressure membrane.
The locating surface may consist of the surface of a flat plate. However, in the event that three-dimensionally (3D) shaped sheets are to be welded together, it is advisable to configure the locating surfaces as a three-dimensionally formed 3D contour that at least substantially conforms to the contour of the car body components to be welded together.
The fastening component may correspondingly comprise or consist exclusively of a flat plate for supporting the hollow body. However, when three-dimensionally shaped sheets are to be welded together, it is advisable for the fastening component to comprise a three-dimensionally formed 3D contour, which at least substantially conforms to the contour of the sheets to be welded together. In this case, it is advantageous to fasten the hollow body to the underside of the 3D contour formed by the fastening component.